OBJECTIVES: To review epidemiological and etiologic aspects of diagnosis and treatment of mood disorders (MDs) in children and adolescents, with a focus on essential information for pediatricians. SOURCES: A literature search on MEDLINE, a review of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, fourth edition (text revision) (DSM-IV-TR), and a critical analysis of current diagnostic criteria and scientific evidence regarding the etiology of mood disorders were performed. SUMMARY OF THE FINDINGS: We identified diverging opinions for and against the proposition of using the same criteria used for adults, as listed in the DSM-IV-TR, for diagnosing mood disorders in children and adolescents. Although there has been much debate in the literature on this topic in the last decade, there remains a concern that there may be a significant under-diagnosis of cases due to differing methods. Several epidemiological studies conducted in pediatric populations using different criteria and methods make it difficult to interpret the data currently published. Although the field of neurosciences has achieved major advances in understanding these pathologies, additional investigations are needed to gain a clearer picture of how genetic and environmental factors interact and influence the origin and severity of the disease and the patient’s response to treatment. CONCLUSIONS: MDs have a high prevalence in childhood and adolescence and have major long-term impacts on sufferer’s lives. There is a need to improve diagnostic criteria, adapting them for the pediatric population, with the objective of making it simpler for clinicians, particularly pediatricians, to make diagnoses and initiate early intervention. Advances in the area of epigenetics may aid in the development of new preventative, diagnostic, and therapeutic approaches.